Clarify a notion in topology of spectral spaces

Thanks to Bhargav Bhatt and Ofer Gabber
Descent data in terms of groupoid schemes
A couple of lemmas on existence invariant opens

Thanks to Bharhav Bhatt and Ofer Gabber
Effective descent is Zar local on top
Ind-quasi-affine morphisms

Notion due to Ofer Gabber
Thanks to Ofer Gabber and Bhargav Bhatt
Effective fpqc descent for ind-quasi-affine morphisms

Due to Ofer Gabber
Thanks to Ofer Gabber and Bhargav Bhatt
Algebraic spaces are fpqc sheaves

Due to Ofer Gabber
Thanks to Bhargav Bhatt and Ofer Gabber